Van der Waals Frictional Drag induced by Liquid Flow in Low- Dimensional Systems

Frictional drag between quantum wells mediated by fluctuating electromagnetic field

We use the theory of the fluctuating electromagnetic field to calculate the frictional drag between nearby two-and three dimensional electron systems. The frictional drag results from coupling via a fluctuating electromagnetic field, and can be considered as the dissipative part of the van der Waals interaction. In comparison with other similar calculations for semiconductor two-dimensional system we include retardation effects. We consider the dependence of the frictional drag force on the temperature $T$, electron density and separation $d$. We find, that retardation effects become dominatin…

Knudsen-to-Hydrodynamic Crossover in Liquid 3He in a High-Porosity Aerogel

We present a combined experimental and theoretical study of the drag force acting on a high porosity aerogel immersed in liquid ${}^3$He and its effect on sound propagation. The drag force is characterized by the Knudsen number, which is defined as the ratio of the quasiparticle mean free path to the radius of an aerogel strand. Evidence of the Knudsen-hydrodynamic crossover is clearly demonstrated by a drastic change in the temperature dependence of ultrasound attenuation in 98% porosity aerogel. Our theoretical analysis shows that the frictional sound damping caused by the drag force is gove…

摩擦控制：速率-状态变量方程的捷径与优化

Control of friction: shortcuts and optimization for the rate- and state-variable equation

本文将控制理论应用于速率-状态变量摩擦定律，提出快速状态到状态协议，可在给定时间内驱动滑块在任意两个稳态速度之间转换，并避免黏滑失稳，同时通过变分方法求解最小化摩擦做功的最优协议。